During the last 100 years diagnosis in laryngology has been largely dependent upon indirect laryngoscopy, which in turn relies to a considerable extent on the subjective impression of the examiner. There has been an obvious need for a good diagnostic procedure for early detection of laryngeal pathology and for evaluation of disease involvement. Recently several investigators have discovered that some acoustic measures such as perturbations in the pitch period of speech or short term fluctuation of the peak amplitudes of a vowel are sensitive to the laryngeal pathology. These facts provide a considerable promise for the development of a new method for detecting and estimating pathologies in the larynx and their further study seems warranted. In addition, much remains to be learned about the patho-physiological mechanism of voice production. An understanding of this mechanism would be a basic component of the informed use of acoustic diagnostic measures. The purpose of the proposed study is two-fold: 1) to further develop a reliable objective method that will facilitate both the early detection of laryngeal disease and the quantitative evaluation of laryngeal dysfunction, and 2) to relate certain acoustic measures to the underlying physiological and pathophysiological mechanisms of voice production and to the perception of voice quality.